Langerhans cell histiocytosis (LCH) is a systemic disease associated with the proliferation and accumulation (usually in granulomas) of Langerhans cells in various tissues.

A pathologic fracture occurs when a bone breaks in an area that is weakened secondary to another disease process such as tumor, infection, and certain inherited bone disorders. A pathologic fracture can occur without a degree of trauma required to cause fracture in healthy bone.